You can use the layer switch and comp setting, however I don't think that is answering his question because I am having the same problem. There is normally a options button in the effect controls in CC Particle World and mine in not there.

I can't seem to find the control settings in Particle World that will prevent particles fading in as they are born and fading out as they die. I can't get them to stay opaque throughout the length of the scene. This causes semi transparent particles to pass by the camera. In addition, particles that are further away from the camera appear in front of particles that are closer causing a surreal effect. using a Custom opacity map improves things a bit as far as opacity goes but then causes some ugly and unnatural particle intersections

We can't help you without knowing your settings. That fade stuff could simply be an unsuitable longevity setting, the wrong rendering could be genuine render errors when moving into the particle cloud, which is a ntural limitation in how CC Particle World actually renders the particles...

Hi - thanks so much for your reply. I've attached my settings, and as inexperienced I am with this particular effect, they may seem bizarre. My goal is to have the particles (in this case an image file with transparent bg) retain their opacity throughout. By the way, I'm using CS6.

You will see a light grey box with a dark grey "curve" in there, similar to particular if you ever used that. You will notice there is a feathered curve in the beginning and end of the box. Click and drag along the top of the box so the whole this is "dark grey", basically you are drawing a graph where horizontally is "time" and vertically is "opacity".

Also, visit Cycore's site. They have some tutorials for the AE stock effects that might help you learn how to use Particle World which, you gotta know, is one of the more complex simulation systems you get out of the box. Also, if you can find them, Brian Maffitt's tutorials for Final Effects (Cycore's early versions) are fabulous.